Lauren Fedor is the chief reporter at City A.M., covering politics, banking and financial regulation.

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Barclays chairman John McFarlane said Brexit would leave the City in a "significantly worse" position (Source: Getty)

Two of Britain's top businessmen have warned that the City will be worse off if the UK leaves the EU.

Mike Rake, chairman of BT Group and WorldPay, and Barclays chairman John McFarlane – who also chairs TheCityUK industry group – told Bloomberg TV today that Brexit would be bad for British business.

"There has already been some loss of investment," Rake said, adding, "There will be more if we start to get into a position where it looks serious that we might leave."

McFarlane said Brexit would leave the Square Mile in a "significantly worse" position and warned that firms in New York would look to take business from London.

Speaking in his capacity as chairman of TheCityUK, McFarlane told Bloomberg that a survey of group’s members found 85 per cent want to remain in the EU, with only four per cent in favour of leaving.

"Our opinion is that the City will be significantly worse," McFarlane said. "The rest of world wants Britain to remain in the EU.

"Foreign organisations use London as their main access to Europe, and we don’t know what the impact of withdrawal will be."

McFarlane also called for a vote sooner, rather than later, in order to "reduce the uncertainty" created by Prime Minister David Cameron's back-and-forth with Brussels.

Cameron has promised to hold a referendum on Britain's EU membership by the end of 2017, after a period of renegotiation. Cameron has said that he hopes to secure a reform deal at next month's European Council meeting.

Both McFarlane and Rake said they expected UK voters would ultimately choose to remain in the EU.

"We have had net significant investment in this country during this period of uncertainty because people are convinced common sense will prevail and we’ll stay," Rake said. "But there has already been some loss of investment, not huge, and there will be more if we start to get into a position where it looks serious that we might leave."

McFarlane's comments come in contrast to those of another Barclays executive, who told MPs last week that the City would retain its status as a global financial centre in the event of Brexit.

Speaking to MPs on the Treasury select committee last week, Mark Astaire, vice chair of the investment banking division at Barclays, said that while London has "thrived" within the European Union, the Square Mile would "continue to thrive" outside of the 28-country bloc.

"It’s a great success story, the City of London," Astaire said at the time. "It’s one of our leading industries, and it’s clearly the European leader.

"Do I think that if the UK was to leave the Union, London won’t be the leading financial centre in 10 years’ time?" Astaire added. "I would have to say no. I think it will."